Preimplantation genetic diagnosis (PGD) is an advanced laboratory procedure in which embryos are screened for genetic diseases or chromosomal problems prior to placing them in the uterus. Introduced in the 1990s, its initial purpose was to help patients avoid passing genetic diseases, such as cystic fibrosis or Tay-Sachs, to their child. It has been shown to be very effective for this purpose, and more recently, its indications have expanded. For example, it has also become a screening test for aneuploidy, which is an error in cell division resulting in an embryo with an incorrect number of chromosomes, either too many or too little. Chromosomal abnormalities are the most common cause for miscarriage in the human population and are often a reflection of reproductive aging (otherwise known as the female “biological clock”). Couples utilizing preimplantation genetic diagnosis would have their embryos evaluated prior to embryo transfer and only the most genetically normal embryo(s) would be selected. It is a relatively complex procedure that involves manipulation of the embryo, so it is offered judiciously to patients in situations where the benefits outweigh the risks.
Patients who believe they are candidates for PGD should schedule a consultation with a physician separate from their new patient consultation. At that consultation, detailed information (including risks and benefits) will be reviewed and their treatment strategy will be individualized based on their situation. Considering this procedure involves an embryo biopsy, which is equivalent to surgery on the embryo on a microscopic level, there is approximately 1-3% chance that the embryo will be harmed. Having an experienced embryologist perform the biopsy minimizes this risk.
PGD has also been recently used as a tool to prescreen embryos in patients over 35 for chromosomal abnormalities in order to help the embryologist and physician choose the best embryo(s) to place into the uterus. Utilizing PGD in this context is somewhat arguable and should only be performed after extensive counseling.
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